Inhalation-activatable dispensers for use with aerosol container assemblies are known, their general purpose being to afford proper co-ordination of the dispensing of a dose of medicament with the inhalation of the patient thereby allowing the maximum proportion of the dose of medicament to be drawn into the patient's bronchial passages. Recently breath actuated mechanism (BAM) or inhalation-activatable dry powder inhalers which combine the benefits of a dry powder inhaler with the convenience and ease of use of breath actuated mechanism are disclosed in some patents such as U.S. Pat. No. 5,408,994 and U.S. Pat. No. 6,880,555.
U.S. Pat. No. 5,408,994 relates to an inhalation device for administration of aerosolized medicament to the respiratory system of a patient comprising a housing defining a patient port in the form of a mouthpiece and an air inlet, the housing containing means for dispensing a dose of aerosolized medicament, an inhalation-activatable triggering mechanism for initiating the dispensing means, and reset means. The triggering mechanism comprises a vane mounted for pivotable movement between closed and open positions, the vane being positioned within the patient port such that inhalation through the patient port generates airflow from the air inlet to the patient port causing pivotable movement of the vane. The device further includes an activator component moveable between a restrained position and a dispensing position which movement causes dispensing of medicament from the dispensing means, the activator component being biased towards its dispensing position. This positioning of the vane in the mouthpiece has the disadvantage of the medicament getting deposited on the vane, leading to a probability of a sub-therapeutic dose as well as increasing the chances of microbial growth on the deposited particles on the vane.
U.S. Pat. No. 6,880,555 relates to an inhaler for medicament in powder form with an opening intended for inhalation. The powder medicament is arranged in the inhaler in a number of enclosures, each enclosure including a specific dose of medicament. A member is provided for enabling access to the dose of medicament. The member is arranged and designed such that it is able to be inserted inside the enclosure and establish at least one outlet passage, between the interior of the enclosure and the inhalation opening, through which outlet passage the medicament is delivered to the patient upon inhalation. It is disclosed that the elongate member serves as a source for air to enter into the interior of the inhaler and also the passage of the medicament from the enclosure into the respiratory tract of the patient. The inhaler is further provided with an activating means comprising a flap pivotally arranged adjacent an air intake and designed to be able of closing the air intake. A pressure spring is arranged for urging the flap to a closing position. Upon inhalation, air is forced through the passage of the elongated body from the interior of the inhaler, creating a pressure drop there and pressure difference between the interior and outside the inhaler. The pressure difference causes the flap to move around its pivot axis, thereby opening the air intake. The pivoting action of the flap causes the cantilever to pivot around its pivot axis, whereby the elongated body is pushed forward by its spring force, and its front end penetrating the blister cover of the blister placed in the wheel in a position in the longitudinal direction of the elongated body. This device has certain disadvantages. The primary disadvantage is the close association of the flap with the air inlet hole, which makes the device susceptible to triggering of the BAM and dispensing the dose even without inhalation if some external object were to exert a force on the flap through the air inlet hole. Additionally the device would be prone to clogging because of the air passageway through the narrow elongated body.
U.S. Pat. No. 6,948,494 relates to a medicament container to be used in a medicament inhalator, which is configured to improve entrainment of the medicament in the air and to improve deposition of the medicament in the lungs, comprising an upper layer and a bottom layer with medicament disposed there between. The upper layer is punctured to provide first and second openings to allow airflow to enter and exit through the upper layer of the medicament container. In a preferred embodiment, the medicament container has a projection which forms an elbow-shaped medicament containment/flow channel between the upper layer and the lower layer.